Method for manufacturing OLED/PLED displays by using solution processes has many advantages and potentials such as low cost, high yield and capability to easily reach large size, and is a potential development direction of the OLED technology.
In the OLED/PLED technology, it is required to use an organic or inorganic material to manufacture a pixel defining layer, to define an organic material for emitting light within sub-pixel regions defined in the pixel defining layer, so as to achieve high resolution and full color display.
In the prior art, as shown in FIG. 1(a), when an organic light emitting device is manufactured by using inkjet printing or nozzle printing, an anode 102 is usually formed of an hydrophilic transparent conductive film (such as ITO film), and for a good attachment with the anode 102, the solvent for forming an organic light emitting material layer 104 (including a hole transport layer and a hole injection layer) is also hydrophilic. However, the pixel defining layer 103 is usually formed of positive photoresist. Since the pixel defining layer 103 is formed of positive photoresist, after being exposed and developed, the pixel defining layer 103 may have an inverted trapezoidal shape (which is wide at top and narrow at bottom which has a proper slope angle and thus may reduce breakage of the organic material film layer or the cathode film layer. However, the positive photoresist has hydrophobicity, resulting in poor attachment between the hydrophilic organic material solvent and the hydrophobic pixel defining layer, the formed organic light emitting material layer 104 may contract and thus the cathode 105 and the anode 102 may have a short circuit therebetween, causing adverse display of the display device, and it should be noted that, in the figure, 101 represents the substrate.
In the case that the pixel defining layer is formed of negative photoresist, both the pixel defining layer and the organic material solvent are hydrophilic, avoiding the contraction of the organic material, and thus restraining short between the cathode and the anode. However, the pixel defining layer formed of negative photoresist has a regular trapezoidal shape (which is narrow at top and wide at bottom), as shown in FIG. 1(b), the slope angle of the regular trapezoid is improper, so that the cathode is intended to be open, thus resulting in adverse display of the display device.